Pleiades

[martin_h]

How would one go about capturing something like the Pleiades, retaining the nebulosity without blowing out the stars?

[steppenwolf]

So much depends on the equipment in use but an 80mm refractor and a DSLR with exposures of between 5 and 6 minutes will capture the nebulosity and the main stars will not bloat out too much. Take lots of images and stack them in either Registax or Deep Sky Stacker, both of which are free. If you find the stars are burning out, take some shorter expoures as well and blend these into the image using a graphics program like PhotoShop (expensive) or 'The Gimp' (free but only 8 bit processing currently).

Have go!

[martin_h]

Ive got this so far with Evostar 100ED DS-Pro and QHY8 cam.

6 subs of 5 mins each....so it looks like I need more?

[steppenwolf]

That is a good start, there is some good nebulosity in there but more subs would make a big difference. The image has a slightly 'purple' tinge to it and I note that there appear to be some halos on the bright stars - are you using a filter somewhere in line, perhaps an LP type of some kind?

[martin_h]

I note that there appear to be some halos on the bright stars - are you using a filter somewhere in line, perhaps an LP type of some kind?

Yes there is an LP filter in line. and I think the purple cast comes from pushing the processing to far (trying to make up for lack of subs!) Also I need a new IR filter

[martin_h]

Ive also noticed on some of the individual subs I'm getting diffraction spikes - internal reflections?

[ollypenrice]

I'm starting on an ultra deep Pleides myself. I'm after the faint outlying dust. Surprizingly I find that I can go for 10 min subs with a fast (f3.9) refractor and CCD camera. When I do a basic stretch the stars do burn out but then I can lasso them in Ps, apply a big feather and do three things. A) lower the curve bit by bit, dropping just the bottom a bit, then moving up the curve, dropping it further and further as I move up. B push up the saturation. Brightness reduces visible colour. C) adjust the colour balance. Changing the curve distorts it a little. I did all the mains cluster stars individually this way, so a labour of love. However, the data was in there. I do think some short exposures to get the main stars smaller will be needed to perfect the image but the method I describe has reduced them very considerably.

And yes, I think internal reflections procuced your spikes. I got a Bahtinov-mask like effect once on M45 but I don't even own one!

Olly

[martin_h]

I'm starting on an ultra deep Pleides myself. I'm after the faint outlying dust. Surprizingly I find that I can go for 10 min subs with a fast (f3.9) refractor and CCD camera. When I do a basic stretch the stars do burn out but then I can lasso them in Ps, apply a big feather and do three things. A) lower the curve bit by bit, dropping just the bottom a bit, then moving up the curve, dropping it further and further as I move up. B push up the saturation. Brightness reduces visible colour. C) adjust the colour balance. Changing the curve distorts it a little. I did all the mains cluster stars individually this way, so a labour of love. However, the data was in there. I do think some short exposures to get the main stars smaller will be needed to perfect the image but the method I describe has reduced them very considerably.

And yes, I think internal reflections procuced your spikes. I got a Bahtinov-mask like effect once on M45 but I don't even own one!

Olly

I'll get some more subs (when I can!) and give your method a bash.